sv^spa-20/sv^spa-pol flies have a similar phenotype to sv^spa-pol flies. sv^spa-20 strongly enhances the bristle phenotype of svⁿ or sv^de in transheterozygotes; in the eyes there is nearly complete loss of bristle shafts, and in other parts of the body, loss or reduction of the shafts of microchaetae and macrochaetae is more severe than in svⁿ or sv^de homozygotes.